This invention relates to thermal sleeves for location on gun barrels and has particular though not exclusive application to such sleeves for the gun barrels of tanks.
Tank gun barrels, particularly those over about 3 inches calibre, tend to be long and consequently there is a tendency for the barrels to distort when they are subjected to differential heating conditions such as occur with, for example, the heat of the sun on one side of the barrel and a cold wind on the other side.
Accurate long range shooting depends upon the barrel being perfectly straight, and, in order to insulate the barrel from the effects of the environment, it has become standard practice to provide one or more thermal sleeves for the barrel. Such sleeves commonly comprise blankets of asbestos and/or glass fibre wrapped around the barrels, and it has been found that the effects of wind, rain and sun on hot gun barrels encased in such sleeves are considerably reduced.
However, thermal sleeves of this type suffer from a number of disadvantages not the least of which is that they are easily damaged and torn by trees and the like during cross-country manoeuvres, while the sleeves are such as to absorb rain water thereby affecting the balance of the gun. Further, such sleeves do not provide an even heat distribution around the barrel, while heat loss from the barrel is significant resulting in poor thermal signature. In addition, the sleeves tend to become adhered to the barrel after prolonged use, with the result that they cannot be reused on replacement of the barrel, while the problems associated with the use of asbestos are well known.
It has been proposed to attempt to overcome some of these disadvantages by providing sleeves of lightweight metal spaced from the barrel to form an air gap between the sleeve and the barrel. However, the weight of such sleeves must be carefully chosen to ensure that they are sufficiently strong to resist mechanical damage but at the same time being light enough not to effect gun balance and inertia. A metal providing such qualities is magnesium. However it will be appreciated that the inflammability of magnesium can pose grave problems on the battlefield.